Final answer:
The nurse should monitor the client for mental status change as an adverse reaction to cimetidine.
Step-by-step explanation:
The nurse should monitor the client for mental status change as an adverse reaction to cimetidine. Cimetidine is a medication used to treat gastric ulcers, but it can have side effects on the central nervous system. Mental status changes may include confusion, agitation, hallucinations, or depression. It is important for the nurse to closely monitor the client's mental state while on this medication.